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\bibitem{hughes} Hughes J. The Design of a Pretty-printing Library. Advanced Functional Programming. Springer Verlag, 1995.
\bibitem{oppen} Oppen D. Pretty Printing. Stanford Verification Group. Report No. 13. Computer Science Department Report No. STAN-CS-79-770, 1979.
\bibitem{wadler} Wadler P. A Prettier Printer. Journal of Functional Programming. Palgrave Macmillan, 1998.
\end{thebibliography}
